Apparatus for treating impure liquids



Feb. 1, 1944. c. REYBOLD ETAL 2,340,342

APPARATUS FOR TREATING IMPURE LIQUIDS Original Filed Dec. 18, 1941 3 Sheets-Sheet 1 ATTORNEY.

3, Sheets-Sheet 2 1944- D. c. REYBOLD ETAL APPARATUS FOR TREATING IMPURE LIQUID Original Filed Dec. 18, 1941 INVENTORS I/Yrw/Y/Jflsmm 00m 621617676111 mdI 9Q Q Q ATTORN 5 Sheets-Sheet 3 D. C. REYBOLD El" AL.

APPARATUS FOR TREATING IMPURE LIQUIDS Original Filed Dec. 18, 1941 mvsmons MTA'M/JF/JC/if/f wanna/firm ATTORNEY.

Feb. 1, 1944.

Patented Feb. 1, 1944 g i APPARATUS FOR TREATING IMPUBE LIQUIDS Douglas C. Iteybold, Northbrook, Ill., and Anthony J. Fischer,

Manhasaet, N. 1.. asllgnors to The Dorr Company, New York, N. Y., a corporation of Delaware Original application December 18, 1041, Serial Divided and this application August 24, 1943, Serial No. 499,812

(Cl. 21H) Claims.

This invention relates to the purification of polluted or impure liquids such as sewage, tradewastes and the like, and this application is a division of application No. 423.430 filed December 18, 1941. In such purification, one recognized method in use today involves the use of a bed of discrete material containing biological organisms which include a wide range thereof from bacterial flora up to animal life as exemplified by worms. The biological organisms are depended upon to convert the unstable and putresclble or septical organics that render the liquid impure into stable innocuous substances. The organisms are also depended upon, at least in part, to render nonsii'iileable suspended solids more readily settlea a The invention has relation to what is known in the sanitary engineering art, as trickling filterbeds. Of late it has come to be accepted that it is desirable to supply liquid to be treated in filterbeds at rates that would have been considered a few years ago as dangerously high. This invention has especial application to high-rate filterbeds. An outgrowth of the high-rate filter-bed is that there be associated with it a recirculation system whereby liquid being treated can be repeatedlyor continually recirculated through the filter-bed. This permits the continuous dosin on the filter-bed of aliquid more uniform in character, and reduces the extreme fluctuations in fiow. In most systems one or more detention tanks are associated with the filter and the recirculation system may be so arranged that filter eilluent is recycled back to the detention tank or primary clarifier preceding the filter; or detention tank or secondary clarifier eiliuent is recycled back to the filter which precedes the detention tank. In either case, the filter is closed at such a rate with liquid containing micro-organisms favorable to the promotion of optimum biological conditions in the filter bed that clogging of the filter bed is avoided due to a continuous sloughlng oi! oi the solids that would normally tend to accumulate. At the same time, the recirculation from the filter to the primary clarifier or from the secondary clarlfier to the filter dilutes the strength of the liquid fed to the filter so that it becomes more amenable to treatment. The detention tank is usually provided with means for mechanically cleaning it of deposited sediment to guard against septlcity oi the sediment, and the tank is one from which overflows-a clarified eitluent.

' In recirculation types or trickling filter plants involving a filter and a clarifier in closed-circuit,

the rate of filter application may be multiples of the rate of new reed incoming to the system. The new feed may be introduced at any suitable point. Likewise, the ellluent may be discharged from the system at any desired point.

Among other advantages realizable, mention is made of the fact that recirculating trickling filter systems gave the unexpected result of permitting the use of filter beds only three feet or less in depth which could be operated at high eillciency. This permits the use of high filter loadings figured as pounds oi B. O. D. per cubic yard of filtering media per day. It has been i'ound that the efllciency of recirculating type filters increases as the amount of recirculation increases. The high rates oi dosing tend to prevent clogging of the interstices between the discrete stone particles oi the filter media; ample food is brought to the immotile biologic organisms of the bed: their excretions are washed away therefrom; and some of the organisms are washed into the clarifier so that biologic oxidizing activity of the saptical organics is continued in the clarifier in addition to the bed where it its initiated. This method of operation also keeps down the filterfiy nuisance and further keeps down the odor nuisance.

The disadvantage of the use of such high recirculation rates, however, is that a large and expensive piping system is required to convey the clarifier eifluent to the trickling filter bed,otherwise a high loss of head will result, possibly requiring the pumping to the beds.

According to the present invention a liquid treating system is employed wherein a relatively shallow bed of discrete material is disposed in encircling arrangement with respect to a liquidreceiving tank of a type which may function as a clarifier. The tank is furthermore of a type having supernatant outflow means disposed about and leading from the upper marginal regions thereof. Also according to the present invention such shallow bed of discrete material functions as a trickling filter-bed extending to an elevation whereby gravitating filter eiiluent can be collected and, according to operative requirements,

' pumped back into the tank substantially against only a minimum or relatively low back pressure head. The top 01' the filter-bed is disposed at elevation sufliciently low so that there can always be realized a gravity fiow or clarified liquid from the supernatant outflow means, to wit. from the region about the upper marginal portion of the tank, and consequent spraying of the gravityconveyed liquid over the trickling filter-bed in a relatively uniform distribution. The use of the shallow bed encircling the tank with its surface lower than the liquid level in the clarifier tank assures the gravity feed to the filter-bed directed from the clarifier through a conducting and distributing means which may be relatively simple and of low cost. This may be through a means embodying a number oi relatively uniformly but horizontally spaced individual pipes extending downwardly from the upper marginal regions of the tank and of which the pipes terminate in spray heads or other suitable liquid diffusing delivering means. Each of these pipes is preferably provided with a valve therein whereb the flow therethrough and therefrom may be adjusted to operative requirements or according to the particular type ofoperation decided upon. The use of a shallow bed encircling the clarifier assures gravity feed to the filter-bed direct from the clarifier through a pipe system of low cost.

In the practice of straight or once-through filtration, over which the recirculating type was an improvement. the overfiowi'rom a primary clarifier passes through the trickling filter where biological sludge is formed and the filter-treated liquid enters a secondary clarifier where separation of the liquid is effected into settled sludge and efiiuent.

The straight filter must be dimensioned and operated to effect as completely as possible the biological purification and coa ulation of sewa e impurities within the interval allowed for a sin le passage through the filter. This necessitated a large volume of filter media and a. depth of the filter which was accepted to be from 6 to 12 feet. This depth was so much the standard that it became a custom with sanitary engineers in specifying filter loads or capacities. to disregard the factor of filter depth as a constant and refer to fileer capacity in terms of area or horizontal expanse only. Then there was accepted for filter capacity or load the dimension "m. g. a. d."; that is, "million gallons per acre per day.

Since the patentees are working essentially with a shallow filter-bed in circuit with a detention tank or clarifier, the invention has for one of its objects an arrangement for the proper integration of these elements while they are concentrically disposed, with the clarifier or detention tank in the center and the filter-bed or beds encircling the clarii'ier. Another object is to modify this arrangement for two-sta e treatment. And a further object is to provide means for returning the filter-bed discharge back to be mixed with the liquid in the clarifier tank. A still further object is to provide means in this assembly for thoroughly distributing over the illter-bed area. the liquid passing thereto. Another object is to make such an assembly into an esthetically attractive design, for sewage-treating short-circuiting.

paratus for dosing the filter-bed direct from a launder of the clarifier.

In connection with recirculation of liquid from the clarifier tank that is in circuit with the filterbed back to the filter-bed, it has been found advantageous to recirculate liquid from the liquidbody that lies within the clarifier tank rather than liquid that has once passed from the tank by overflowing an eilluent weir. Therefore a further object of this invention is to devise a submerged launder for the clarifler from which liquid can be supplied to the filter-bed, especially by gravity and at a constant head.

As illustrative of certain manner in which the invention hereof may be realized, reference is made to the accompanying drawings constituting a part of this specification.

In said drawings- Fig. l is a perspective view illustrating one form of the invention,

Fig. 2 is a vertical sectional view of the form shown in Fig. 1.

Fig. 3 is a vertical sectional view of a form somewhat dififerent from that shown in Fig. 2.

Fig. 4 is a detail of a. submerged weir or launder employed in the form of Fig. 3.

Fig. 5 is a vertical sectional view embodying primary and secondary stages each of which embodies certain important features of the form of apparatus shown in Fig. '2.

In Figs. 1 and 2 the reference numeral ii in dicates generally a clarifier tank having a wall section l2, a bottom or fioor section i3, an upstanding pier II that is hollow and hasa bore I! from which feed liquid for the tank Ii is emitted in a slotted section l6. l1 indicates a baille for deflecting the feed liquid and preventing The pier I4 terminates in a platform I! that supports a bull ring or gear pro viding an annular turntable l9 that is rotated through the medium of a motor 20 and any necessary gearing. The motor is carried on a stationary member i8 extending upwardly from the platform ll through the turntable I! as for example according to the teachings of the Scott Reissue Patent Re. 20,072. Supported from the a turntable I8 is 9. depending cage or drum II from a which at the bottom thereof extend rake arms 22 that are equipped to impel sediment over the tank fioor to a sludge discharge sump 13 that is connected with a valve controlled sludge discharge pipe or conduit 24.

Clarified supernatant liquid in the tank ii I overflows a weir I! that determines the liquid plants are being located increasin ly in parks or other public spaces of municipalities that are more or less'landscaped.

An additional object is the provision of a multiple launder for the cl-arifiergso that efiiuent for release from the system is taken from one launder that is functionally separate or remote from another launder whose liquid is passed for distribu tion over the filter-bed surface.

Another object is to provide an arrangement whereby the liquid from the clarlfier can be supplied to the filter-bed and distributed thereover substantially uniformly while under a constant head. And a still further obiect is to devise aplevel in the tank. and passes into a launder 26 that encircles the tank. Associated with the first annular launder I6 is a further annular launder 2' which makes with launder 26 a combined or double launder that has a common wall 10. Liquid flows from launder 26 at intervals around its length, through a plurality of downflow pipes 30. which may be controlled by valves 3|, terminating in spray nozzles or other liquid distribution means I! located adjacent the upper surface of a trickling filter-bed 33 formed of discrete material or media a such as crushed stone'or rubble that is supported from a permeable latticelike support It and a wall 38 that encircles the tank Ii. The top of the filter-bed 33 is lower than the liquid level of the tank i i. Liquid passes from launder it through conduit 2! controlled by valve 21' to discharge or for further treatment. The floor ll of the filter-bed ll is arranged to drain filter-discharge into an annular trench or sump 30 that has associated with it a wet-well ll from which filter discharge can be removed throush r pe delivers into pipe l6 having a stop valve 8". By closing stop valve 80' the filter emuent can be passed from the filter through a pipe 51 equipped with stop valve 81' if and when the latter is open; or if the stop valve 50* is open and the stop valve 51 is closed, then the pump it will force the filter emuent into the pipe or conduit l3 thence into here I! of upstanding pier It so that the filter giving access to the operating parts of the tank ii. k

Figs. 3 and 4 illustrate a modification or form which differs only slightly from that of Figs. 1

and 2. where'the parts are the same in each,

' the same reference numerals have been used and as to such like parts the previous descriptive matter relating thereto applies and is not being repeated. In this modification the newly incom- 7 ing feed liquid is supplied through thelow pipe or conduit 43 thence to the bore Ii of hollow pier H from whence it passes into the clarifier tank H. Clarified supernatant liquid is released from the tank by overflowing annular peripheral weir 25 into peripheral launder 2| fromwherice the liquid is released or outwardly through pipe 21. In this modification, the second launder is shown as a member on supported from the ba-flle l1. This second launder is in the form of a tubular collector or submerged launder disposed below the liquid level of the tank] i and is protectcd from scum and the like by means of a top cover or strainer plate ii that is preferably periorated to let'strained liquid flow freely into the launder. As shown in Fig. 4, the top strainer plate ii of launder in may also have associated with it a bottom strainer or perforated plate ll.

In fact, this second launder Just described may be viewed as a submerged perforated collecting ring. From this submerged launder liquid passes at intervals through spaced-apart pipes 62 having valves 52' for controlling or adjusting the quantity of flow to a distributing pipe 53 which, is annular in plan and disposed adjacent the top of the filter-bed. This pipe 53 is provided with suitable overflow passage area as by being slotted at M from which liquid is relatively uniformly distributed over the surface oi the filter-bed 83. The centrifugal pump" returns filter-bed discharge through the valve-controlledpipe 58 to the low pipe or conduit". It will be noted, however, that the discharge from the pump can be also pumped to release from the system' through the valve-controlled release pipe ll having the stop valve therein.

The quantity of normal supply of feed to the tank, to wit, the supply of fresh feed to thetank ll by centrifugal pump ll which i The slotted distiibutlns p p I3 is relied upon to" insure a relatively uniform distribution of liquid passing therefrom to and throughout the upper portion of the filter-bed It whereby the thus distributed liquid is caused to trickle downwardly within and throughout the entire bed.

Fig. 5 illustrates a two-stage plant of which the first or rimary stage indicated at A is substantially the same as arrangement of Fig. 2. The

plus the returned or recycled fllter eflluent' passed by the pump 42 into the pipe or conduit 43, is greater than the quantity or liquid which is allowed to flow into the submerged collecting ring and ultimately therefrom toandirom the dis tributing pipe 53 and hence the overflow weir 25 is enabled to function as a means that determines the normal surface level of the liquid in the clarifier tank II. t a

' eflluent will be pumped back into the tank, or

secondary stage of this 5 is indicated at B and is a modified form of the design at A. As

to these two stages where the parts are the same like reference characters have been employed.

In reference to stage B. it will be "noted that normally the liquid is supplied thereto throughconduit 31 into an outer launder I. From this launder the supplied liquid passes downwardly through valve-controlled pipes ill from which it passes into and from distributing heads or means 32 by which the liquid is distributed relatively uniformly over the top surfaceof the trickling filter-bed 33. The liquid trickling from the filterbed 33 is finally received as filter eiliuent in the sump 40. From this sump of the secondary stage 3 filter edluent is passed by pump 42 into and through the conduit 43 and the hollow pier i4 whereby it is ultimately delivered into the liquidholding section of tank ll. Clarified supernatant liquid from this secondary tank ll overflows weir 25 into the innermost launder 28 from which it passes, or from which at least some of it passes through branch pipes 30', by control valves ll therein, into valve-controlled pipes 30 whereby it is distributed through the heads or members 32 of Pipes so.

It will be observed as to this secondary stage B that a partition member 28 is disposed between the innermost launder 26 and an intermediate launder II. The top of this partition member 29 which is circular in plan or of other appropriate formation is at elevation lower than that of the overflow weir 25 and serves to act as an outlying second or intermediate weir that permits an overflow of some of the clarified efliuent from within the launder 26 towards and into launder 28. From th 'latter launder 28 the efiluent is passed to a region remote from the tank through the conduit or pipe ll. Operations that can be carried out in the apparatus in this two-stage plant are typified by the following:

Liquid to be treated passes inwardly through conduit 58 past check valve 58 into conduit l3, thence upwardly through the hollow pier ll of stage A whereby it is delivered into tank ll of stagesA. The clarified liquid from this tank overflows weir 25 into launder 26 from which the overfiowed liquid-or a controlled portion of the overflowed liquid-passes downwardly through valve-controlled pipes 30 by which itiis distributed over the trickling filter-bed l3. Eilluent from this bed passes into the sump "(is pumped therefrom by a pump 42 (a) through a valvecontrolled return branch 58, assuming the valve 58 is open, directly back into the tank II o! the first stage, or (17) into the transfer branch 60, ii

a the valve 59 therein is open, whereby the filter eiliuent, or some of it, may be transferred directly into the pipe 31 leading to the second stage. In other words, at the option of the operator all of the filter efliuent can be pumped through branch 58 back into the tank, or only apart of the filter none of the filter eiliuent need be passed back into the tank of stage A. in other words, if the valve 58 oi this return branch is closed, then all of the iiltereiliuentcanbepassedbythepumpll through the branch OI, assuming the valve I of the latter is open. If valve II in the return branch and if the valve II in branch til are only partially open, then it is possible to give a split passage of the filter efliuent whereby some will be returned to the tank i l and some will be transferred through the branch Cl directly to the pipe 31 leading to the secondary stage B.

It will also be observed that the partition 29 between the inner and outer launders 2C and 28 is lower than the weir 2! whereby if desiredaccording to the position of the valves Ii in pipes ill-none of the overflow past weir ll will pass partition 20, or some portion of or all of the overflow past weir I! can be caused to pass over the partition 28 as a secondary overflow into the outer launder II from which this twice overflowed liquor can pass through valvewontrolled pipe fl into pipe II for gravity flow and delivery into the launder 88 of the secondary unit B. From the outer launder DI the liquid is distributed directly over the filter-bed by the valvecontrolled pipes 30. Filter eilluent is pumped from the sump ll of the secondary unit into the tank ll thereof. The clarified liquid from this secondary tank H overflows the weir 25 and a portion thereof can be optionally passed back to the trickling filter-bed by means of the valve-controlled pipes II that lead as branches into the distributing pipes 80 while another passes the intermediate-partition or secondary overflow member II into the discharge launder II and therefrom released from the apparatus. One valve is located at I4 and another at I I" in the respective conduits leading to the hollow piers of the tanks of the primary and secondary stages. By closing the valve ll of the primary stage it is feasible to pass incoming liquid supplied for treatment directly to the second stage whereby the operations of the first stage can be eliminated and the trickling filter treatment can be carried out entirely at the second stage. Sludge from the tank of the second stage is passed by the pipe I, pump Ii and pipe I! as return sludge that is delivered to a section of the pipe ll leading to the primary stage.

with respect to the apparatus of Fig. 5. it has heretofore been pointed out how the secondary stage can be employed as a single unit. It is now to be noted that the outer wall of the outlying launder ll of the secondary stage B extends to an elevation higher than that of the rising wall or partition between the outlying launder l8 and the intermediate launder 2|. If for any reason it is desired to temporarily employ only the primary stage A as a sludge treating unit this can be accomplished by closing valve is" in the feed line leading to the tank of stage 8 and by closing the valves 3| and II of the pipes I. and II of stage B, allowing the effluent to pass from stage A through the pipe ll into the outlying launder of stage B, thence as overflow past the wall between the launders II and ll and from the latter as eilluent released from the system through pipe l'l,

In connection with each of the combined settling tanks and trickling filter-bed units shown in the drawings hereof, it will be noted that the depth of each trickling filter-bed is relatively shallow as compared with the depth of the tank. As shown the construction providing the bottom or floor of the trickling alter-bed is shown practlcally as an extension of the bottom of the tank. with this arrangement a feed-supply pipe or iniiuent conduit such as II can. without undue excavation, be located so as to extend below the floor of the filter as well as that of the settling tank.

The elevation of the top surface of each trickling filter-bed is substantially lower than that of the surface level of the liquid in the tank with which it is associated, or, as otherwise expressed, lower than the launders from which liquid is gravitationally passed through valve-controlled downflow pipes such as 30 and ii for distribution over the top of the bed.

In Fig. 3 the launderor submerged pipe from which the liquid isllipplicd to the bed through the valve-controlled downiiow pipes I2 is not disposed directly over the trickling filter-bed. However, it is located so that there is a gravital downilow of liquid from within the tank through the pipes I2 and ultimate distribution of the liquid over the bed. In the instance of each form illustrated the height available for effecting this gravitational transfer is substantially that difference in elevation between the upper surface of the trickling filter-bed on the one hand and the elevation or approximate elevation of the overflow weir II; This diflerence in elevation or static head available is preferably of the order of from 3 to 4 ft. of water. w The structure shown in Pig. 2 or the structure shown in Pig. 8 can be readiiy substituted for the corresponding subcombipatlon shown in Fig. 5:

(a) By merely connecting the pipe 21 of either Figs. 2 or 3 to the pipe section 31 leading to, the outside launder 8' of Fig. 5; and

(b) By substituting for the curved portion or section of the pipe or conduit ll, of either Figs. 2 or 3. a 'i' pipe section and valve substantially like that indicated in Fig. 5 by T pipe section II and the val e with such changes it i be manifest how the apparatus or structure of Figs. 2 or 3 can be operatively incorporated in the arrangement of Fig. 5. While the launder or pipe ll of Fig. 8

' is submerged. it will be manifest that the gravitational flow therefrom downwardly through the pipes 82 can be controlled as to quantity delivered to the trickling filter bed served thereby by adjusting the valves if of said pipes, to wit. in a manner like that obtained by adjusting the valves 8! of Figs. 1, 2 or 5 whereby to control the quantity or rate of downward ilow through the descending pipes 30. The valve control pipes 30 of Figs. 1, 2 or 5 and the valve-controlled pipes I! have corresponding functions and relationships.

We claim:

1. Apparatus for treating impure liquids comprising in operative combination a settling tank equipped with means for transferring sedimented material therefrom; a set of inner and outer marginal launders of which the inner launder is disposed for receiving as efliuent supernatant liquid overflowing from the tank and of which the outer launder is disposed for receiving as splitofl eiliuent a quantity of liquid overflowing from said inner marginal launder; atrickling filterbed of discrete material surrounding said tank: meansprovidingafloorstructuroforsaidbed and having a sump for receiving filter efluent gravitating thereinto; valve-controlled downilow means for passing liquid from said inner marginal launder and for distributing the thus passed liquid over the trickling filter-bed; feed-supply means for passing to said tank liquid to be treatfilter-bed having a bottom that discrete 2,840,842 edmumliinsmeansrorpsssinsniteremuentrrom .fl terme ul rlrdisi ar th clarigfldynmpmkwflummdmmfopmnerwiththetopoithenltermediaatageneral inlllqllldlmmtheoutirlaunderalong pathelevationbelowthltoitho liquidlevelinthe wayleading tromtheunit. clarinet. a main section in said bottomwncrein 2. Apparatus as defined in and by claim 1, g accumulates liquid thathas trickled through the ham wanted with 5m, pumping mm filter-bed; means tor continually adding liquid valve-controlled branches of which one branch from the il mum to t cl 'i'; and a P serves to optionally conduct the pumped liquid railty oi flow pipes extending outwardly irom the o M w the tank and other sag-yes to opflonany olariiier to the iliter bed 8PM to distribute conduct-pumpedliquid from theunit. is liquid by aravitv new from the launder means 3. Apparatus for treating impure liquids com- 5 oolrelllondinl area! mining in operative combination a settling tank 01 fi in w i plm l un having means for transferring sedimented mameans e t d marginally a n the top portion tcrlsl-tncroirom; meansassociatedwlthsaidtank the Mr and comma a psr tlon a w ll providing inner, intermediate and outer marginal is mm the 9 0! We launder and launders of which the inner launder is disposed at n e v tion lower than the overflow for receiving as eiiiuent supernatant liquid overt" the c194111315 881d P 8 Wail d flowing from said tank, or which the interme- 8 an i r and anputer launder section, the diate launder is disposed for receiving as splitminder t n adapted to receive the P 1- 01! eiliuent a quantity of liquid overflowing irom :9 my overflow m th clll-flfler and having sunthe inner launder, and oiwhich the outer mar new!!! therewith" sa d pip s for passing clarifler ginai launder is normally functionally separated a liquid by avity now to the inter bed. from the intermediate launder; a trickling fllteri launder Section D 1 8 adapted to rebed oi discrete material disposed about t tank; excess clarified liquid overflbwms sa d l mem providing a supporting fl r f r 1 mm titioning wall from said inner launder section and bed and having a depression therein aflording mm with s efliuent outlet means. a receiving sump ior filter-bed emuent gravitatins Appamtm impure iquids comthereinto; means for passing feed liquid to be mmmmn P i ry and treated to the outer launder; valve-controlled B station? W of which the p im y means by w ich liquid is trsnsierrcd from the Won-includes a settling tank equ bped with outer launder for distribution over the trickling mm transfefl'ml imented material filter-bed; valve-controlled means by which sumerelmm. a et 0! inner and outer marsin i pernatant overflowing liquid iroln the settling launder which the launder 18 disposed tank is transferred fromthe inner launder and receivmi liquid fl wing from the tank distributed over the trickling filter-bed; means and which the WW under 18 disposed f r loipassing filter eiiluent irom the sump to the l 8 t ty or liquid overflowing from tank; and means leading from said intermediate said inner launder. a m ns alter-bed or dislaunder {or releasing liquid as treated eiiluent 3 P lurmufldlni s id tank. means proiosvlng tile unitJ c for, said had nd havin 4. Apparatus for the treatment oi impure liil- 40 a sump realms filter disc arge gravitatins uids polluted with septical organicscomprising a therein. ans for conduct-ins liquid from said mechanically cleaned clarifler provided with a under and fl il he liquid over sediment discharge outlet, means ior supplying the 8 miter-bed. ee 99 3 means for impure liquid to the apparatus, means determln- P 8 liquid to e treated to said tank, pumping the liquid level in the clariiier, launder means 3 8 P mp inlet connection between the ror receiving liquid irom the clarifler, outlet P s means and the sums. a valve controlled means for releasing treated efliuent from the ap- Pump auction for p l y Passing paratus; a trickling filter-bed having a bottom liquid m the ms and item the pumping that supports discrete filter media annularly dlsmeans back W the nd valve controlled posed around the clarlfler with the top or the means P y p g quid from filter media at a general elevation below that said and laid Pumping means to an outer oi the liquid level inthe clariiier, a sump section P the P unit; and (b) which in said bottom wherein liquid that e secimdlry t ion includes a secondary Bothas trickled through the filter-bed; meanri'oi' l $511k u pped with means for transferring continually passing liquid irom the sump section Bedimenwd material therefrom: a set f inner. to tho clcriii r; and a plurality or flow pipes 'miermedme d Outer i unders or which the inoztendin; outwardly from the launder means to launder 18 filmed or r eiving as liquid the alter-bed adapted to distribute liquid by gravfrom the ndary tank, or which 7 it; flow from the launder means substantially P is disposed for receivuniformly to corresponding areas or theillter bed. o 8 as split-oil eflluen't a'quantit ofliqum said launder means comprising one'launder to 110M118 mm the r sponding inner launder, which the outlet means is connected and a second and or which the outer launder is iunctionaily launder submerged in the clarifler liquid lroin separated from the intermediate launder, u seewhich clarifler liquid to the filter-bed trickling filter-bed or discrete material throuahsaid gravity flow pipes. e5 m -i i the m irtank. moans providing 5. for f impure liq. a floor structure 10155111 secondary filter-bed and uids polluted with septical organics comprising a i g a sump for receiving iilter discharge mymechanicelly-eleaned clariiier' provided with a k PM!!! wns ding from the outer sediment discharge outlet, means fol-supplying launder or the secondary unit and .ior distribimpure liq d tonic apparatus, means determin- 10 w s t liq id over the secondary trickling in; the liq level in the clariiier, launder means filter-bed, means'leadina iron the inner launder ior receiving liquid iron: the clarifler, outlet of the sec dary unit and'tor distributing the means connected to'said ciarl lcr icr releasing liquid conveyed thereby over he s condary tricktreated eflluent ironi the apparatus, a trickling ii filter-bed. and transier means 1 passing liquid from said secondary filter-bed sump int seiiieeoondm tank: and momma also oomtion leedin irom enoi'timoitheteed-lunniy prising means ior conducting liquid from the mega: that is mormmvememn treating eteze.

outside 01' the apparatus. l0. Abneratm tor the treatment of impure liq T. Amtue for tmtlng impure liquids oomuide polluted with septic: manic; mm a prising a two-ltlse plant 01' which each stage cllrifler provided with e lediment discharge outcomprises a cleriner tank and a circumjeeent I let. a feed conduit tor ml to the interior of trickling filter-bed having a bottom that supports the cleaner impure liquim eunplieg tor treatment discretenitermedie,a.einnpeeetioninseidbotintheopparatmacheckvelveineeidieedoonthe clarlfler tank, mum melm for dete mini g in: a blckwlrd flow through the conduit, a supernatant liquid outlet meme a. member liquid overflowing therein from the tank, gravity that determinee the liquid level in the clan-flier.

tributing such liquid thereover: said two stages being supplemented by menu for supplying reed bed Md 8 bottom ting 16 d. a lump uid to the tank of the primary sta e, means section in d bottom wh in wm htee liqumtemn nqmdtmthamundermem uidthnttriekieei'romthefllterbemeiiltereflluoithenrimerytmktotheiaundermeaneotthe ent trenetermeem lmlmpi r-onnsecondary tank, and mum for releasing treated Mn: efluent m theme section l quid i'romtheeeeonderyltue. and having e .pum MW liquid mpemntmtiiquidwtietmelmendror dumb- 9. Apparatuaaceordingtoclnim'haooordm m utimitovertheiilterbed. whicg1 there is provided 1 velve tor dmttmg oil 0 any recteuppiyoi'moomingliquidtothepri- M -AB .RIYBOLD. marytank and in which there is I. conduit lee- THONY J. 

